1. Field of the Invention
This invention relates to devices with nanoclusters.
2. Description of the Related Art
Some devices such as memories (e.g. non volatile memories) utilize discrete charge storage elements called nanoclusters (e.g. of silicon, aluminum, gold, or germanium) for storing charge in a charge storage location of a transistor. In some examples, the nanoclusters are located between two dielectric layers, a bottom dielectric and a control dielectric. Examples of such transistors include thin film storage transistors. A memory typically includes an array of such transistors. Examples of nanocluster types includes silicon nanocrystals, germanium nanocrystals, gold nanoclusters, and aluminum nanoclusters. In some examples, nanoclusters are from 10-100 Angstroms in sized and may be of doped or undoped semiconductor material or made of conductive materials.
Some memories that have charge storage transistors with nanoclusters are implemented on integrated circuits that also include high voltage transistors in the circuitry used for charging and discharging the charge storage locations of the charge storage transistors. Charging or discharging the charge storage locations is used to store one or more bits of information, and may be referred to as programming or erasing. These high voltage transistors typically include a relatively thick gate oxide. This gate oxide may be grown by a steam oxidation process. This steam oxidation process may penetrate the control dielectric of the charge storage transistors thereby undesirably oxidizing the nanocrystals and undesirably increasing the bottom dielectric thickness.
What is needed is an improved method for making a device with nanoclusters.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted. The views shown in the Figures are not necessarily drawn to scale.